Method of and apparatus for slag control



R. S. BABCOCK METHOD OF AND APPARATUS FOR SLAG CONTROL Filed June 8, 1940 ROGER S. BABCOCK ATTORNEY Patented Nov. 17, 1942 METHOD OF AND APPARATUS FOR SLAG CONTROL Roger S. Babcock, Plainfield, N. J., assignor to The Llnde Air Products Company, a corporation of Ohio Application June 8, 1940, Serial No. 339,451

Claims.

This invention relates to thermochemically treating ferrous metal work and particularly, to an improved method of and apparatus for controlling molten slag as it emerges from a thermochemically treated zone to facilitate its removal from the work,

It is well known that ferrous metal, such as iron or steel, when heated above ignition temperature, combines with pure oxygen so rapidly that it actually burns. Thus, if a spot one piece of metal is heated to ignition temperature and subjected to a jet of oxygen, the iron will burn vigorously. Heat is generated as the iron and oxygen combine to form iron oxide, 8. material that is solid at ordinary temperatures, but which melts at a temperature somewhat below the melting point of iron or steel. The heat generated by the burning iron is sufiicient to melt the iron oxide so that it runs off as molten slag exposing more iron to the oxygen jet, The jet can thus be moved along to produce a clean cut or groove.

Conventional thermochemical working of this character involves the use of a blowpipe which has in addition to a central opening that sup-. plies the oxygen jet, means for producing a number of small oxy-acetylene heating flames. From two to six of such flames are generally arranged symmetrically around the central opening in the nozzle of the blowpipe,v The preheating flames generally remain burning while the thermochemical working is in progress in order to make up for the radiated heat lost at the surface. It is well known that such oxy-acetylene working pro-. vides a rapid and economical method of deseaming, desurfacing and severing steel, wroughtiron, cast iron, and the like. Because oxy-acetylene cutting is a thermochemical process, the thickness of the metal to be cut imposes relatively little diificulty as compared with mechanical processes of severing.

However, when ferrous metal bodies are flame cut with the aid of an oxygen stream, slag is produced by the thermochemical reaction most of which flows downwardly through the cut or groove and falls away from the work. Some of the liquid slag tends to collect on the surfaces of the work immediately adjacent the bottom edges of the kerf. Slag accumulations or formations of this nature are undesirable and particularly troublesome when the work is cut at a relatively high rate of speed while the work is hot, because they adhere quite firmly to the severed work and heretofore have been removed only with great difiiculty and expense.

In tube mills, when ingots are hot rolled into I billets and then into bars in a steel mill, the work becomes elongated and is usually cut up into convenient pieces of relatively short lengths while the metal is hot. Such pieces are subsequently pierced while hot and it is highly desirable that atleast one end of the pieces be clean cut for the subsequent piercing operation. Cutting the pieces thermoohemically'while the work is hotcauses a large portion of the resulting slag to gather on the under side of the cut edges, which subsequently solidifies and tenaciously adheres thereto. Such adherence is thought to be due to the fact that the slag formation contains a relatively large percentage of unoxidized molten metal mixed with molten iron oxide, and due to the fact that the surface metal of the work is hot and therefore more easily melted. The slag adhering to the surface on which it collects is very diificult to remove and since such removal is usually necessary before the severed piece of the bar can be subse-- quently worked, the cost of this operation is considerably increased.

It has been proposed to remove such slag formationsfrom the'work while the latter is relatively hot by means of apparatus into which the severed workpiece is forcibly moved against a spring loaded arm which reacts to force the work backwardly across a shear which mechanically cutsthe undesirable slag accumulation from the work. While such known apparatus is more efficient and economical than the prior conventional practice of allowing the severed piece to cool for the purpose of mechanically chipping or grinding off the slag accumulation, nevertheless it is not entirely satisfactory because of the large forces involved and because the shear itself is subject to slag accumulation due to its hot conits removal from the work; apparatus for thermodition.

Therefore, the main objects of this invention are to provide an improved method of and apparatus for slag control in thermochemically cutting work, such as ferrous metal bodies, which solves the problems of the prior art; apparatus for controlling slag emerging from a kerf formed by thermochemically cutting work to facilitate molten slag in thermochemically cut metal which facilitatesthe removal of all of the slag formed by the thermochemical cutting treatment. I

In accordance with the invention there is provided apparatus for controlling molten slag as it emerges from a zone formed by thermochemically treating work, comprising slag chilling means provided with a space for receiving the slag as it emerges from such zone to facilitate its removal fromthe work. The slag chilling means preferably comprises chill members adapted to contact the work to be treated along opposite edges of the treated zone, the chill members being conformed to the shape of the work in contact trolling the resulting slag, which comprises a.

cutting blowpipe mounted for movement above the work to be cut, slag controlling means mounted for movement under the work to be cut, means, such as a'carriage, for controlling the movement of the cutting blowpipe to sever the work, and means, such as a bracket mounted on the carriage, responsive to the movement of the cutting blowpipe for moving the slag controlling means, the arrangement being such that the slag emerging from the cut is progressively cooled as the work is severed.

In accordance with the invention there is provided a process of slag control, in thermochemically working metal. which comprises deflecting the slag from the metal and simultaneously chilling it. More specifically, there is provided according to the invention a process of severing work, such as iron or steel, which comprises cutting the work while hot with a stream of oxygen, and subjecting the work while being 'cut by the stream of oxygen to chill. means for controlling the resulting slag.

In another aspect in accordance with the invention there is provided a process of chilling slag as, it emerges from the'bottom of a kerf formed by thermochemically cutting work which comprises progressively confining and cooling the slag as it emerges from the kerf.

The novel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. The in-- vention itself, however, both as to its organization and method of operation, together with further objects thereof, willbest be understood by reference to the specification taken in connection I with the accompanying drawing.

Figs. 1 and 2 are side and end views, respectively, of apparatus for thermochemically severing round bars while controlling slag in accordance with the invention;

Figs. 3 and 4 are views similar to Figs. 1 and 2, respectively, of apparatus for cutting square bars while controlling slag in accordance with the invention; v

Figs. 4a and 4b are sectional views.of-modiflcations of the apparatus shown in Fig. 4;

Fig. 5 is a view mainly in elevation of a slab cutting machine embodying features of themvention;

Figs. 5a. and 5b are sectional views of modifications of the apparatus shown in Fig. 5;

Fig. 6 is a view in end elevation of a thermochemically cut round bar, showing the resulting slag formation before being sheared therefrom;

Fig. 7 is a view similar to Fig. 6 after the slag formation is sheared from the severed work; and

Fig. 8 is a view in side elevation of a severed bar, showing the shape in which slag hardens between the chill plates. Heretofore, in the oxy-acetylene process of cutting ferrous metal bars, slag, consisting of free iron in solution with one or more of. the iron oxides, was emitted from the bottom of the kerf. and adhered to the base metal in harmful slag formations under the work. The slag adhering in such manner was very difiicult to remove and since such removal was usually necessary before further working of the severed bar, the cost of such operation was material. The purpose of the present invention is to provide a novel method of and means for so controlling the slag as it emerges from the kerf that its removal from the base metal is a comparatively rapid, simple and inexpensive operation.

Referring particularly to Figs. 1 and 2 of the drawing; there'is illustrated a round bar R of ferrousmetal positioned for severance by a cutting blowpipe l2 which is adapted to produce a transverse'kerf l3 in cutting the bar R. Chill plates M and I5, conformed to fit the round bar R, are arranged below the latter in parallel relation to and 'on' opposite sides of a vertical plane in which the oxygen stream from the. cutting blowpipe I2 is adapted to travel. The chill plates l4 and i5 may be cooled by any suitable fluid, such as water, through an inlet tube l6 which is connected to a suitable source of supply and is adapted to deliver the cooling fluid to arcuate tubes I1 and I8 arranged on opposite sides of the chill plates l4 and I5, respectively. The tubes l1 and i8 are closed at their outer ends and are provided with a series of small holes IS on their inner side for the discharge of the cooling water supplied thereto, to maintain the plates l4 and I5 sufficiently cool to prevent the transfer of heat from the molten slag and the heat of combustion from melting them. If the cooling fluid is sprayed on the plates, as shown, suitable aprons 20 may be used to prevent the cooling fluid from reaching the work R being severed.

In considering the operation of the apparatus shown in Figs. 1 and 2, as the cutting blowpipe I2 moves transversely above the bar R to sever the latter thermochemically, the kerf I3 is formed, and molten slag emerging from kerf I3 is forced to flow downwardly between the chill plates 14 and I5. These plates, being externally cooled, cause rapid solidification of the slag, in which condition it may be easily broken 'or sheared from the base metal of the bar Rf Upon completion of the cut, the slag thus formed is removed fromthe work by any suitable mechanical apparatus.

Referring to Fig. 6, there is illustrated a slag lamination or sheet F formed in accordance with the operation of theapparatus shown in Figs.

1 and 2, the slag sheet F being shown unsheared constituting the bar R.

Fig. 8 shows the shape in which the slag F, F hardens between the chill plates below the bar R.

in a vertical baffle 4|.

1 asogeza Referring to Figs. 3 and 4 there is illustrated apparatus embodying features of the invention for controlling the slag while thennochemically severing square work, such as square bars S of ferrous metal. The apparatus shown in Figs. 3 and 4 is essentially similar to that described above in connection with Figs. 1 and 2, except that the chill plate means |4, |5 are conformed to the square shape of the work S in contact therewith.

While the water cooling system shown and described above in connection with Figs. 1 to 4, inclusive, has proved to be satisfactory in use, nevertheless, various other methods and apparatus may be employed for keeping the chill plate means cool without departing from the invention. For example, the plates l4 and I5 may be constructed with a cooling jacket 36 mounted thereon, as shown in Fig. 4a, or may even be hollow, as shown by Fig. 41), plates M and IE, to allow the cooling fluid or other cooling medium to pass therethrough. In Fig. 4b the hollow plates l4, |5- are also shown disposed in spaced divergent relation.

Referring to Fig. 5, there is illustrated a modification comprising a machinefor thermochemically cutting fiat work progressively along a predetermined path while controlling the molten slag as it emerges from the cut in accordance with the invention. The apparatus may comprise, for example, a conventional cutting blowpipe 22 which is mounted for vertical adjustment on a bracket 23 supported by a carriage 24 provided with an arm 25 on which is mounted, for horizontal adjustment, a counter-weight 26. The carriage 24 is mounted on wheels 2| which are adapted to traverse rails 21, 21. The rails 21 are supported by a base 28 which rests on the work, such as a slab P, which is to be cut by the-thermochemical severing action of the cutting blowpipe 22.

The bracket 23 is preferably provided with an extension 29 on which is mounted an arm 30 carryingchill block rolls 3|, 3| for progressive movement under the slab P as the latter is cut by the operation of blowpipe 22. The chill block rolls 3| are preferably spaced to provide a vertical slot 32 for receiving the slag as it emerges from the kerf 33, and may be provided with any suitable internal or external temperature controlling means, such as a cooling fluid circulated therein, as shown by Fig. 517, or flowed thereon, as shown by Fig. 5a, from a sprayer 58. For suitably spacing the rolls 3|, the arm 30 has a portion 34 of U-shape, the web 35 of which is .i

horizontally spaced from the vertical projection of the blowpipe 22.

In Fig. 5b, the hollow roll 3| is journalled to arm 30 and to a coupling 31 which is secured to arm 30 through a member 38 having a set screw 39 engaging the coupling 31. Extending from the coupling 31 is a horizontal partition 40 projecting into the hollow roll 3| and terminating Thus, cooling fluid from a pipe 42, flows through an inlet passage 43 in coupling 31 into roll 3| above partition 40, around baflle 4|, through an outlet passage 44 in coupling 31 and finally out of a pipe 45.

' In considering the operation of the apparatus shown in Fig. 5, movement of the carriage 24 on the rails 21 is at such a rate that the gases discharged by the cutting blowpipe 22 thermochemically sever the slab P progressively along a kerf 33 that is substantially parallel to the rails 21. The chill block rolls 3| proceed with the formation of a kerf 33 while controlling the slag as it emerges therefrom; movement of the chill block rolls 3| being directly correlated with movement of the cutting blowpipe 22 and hence in accordance with the formation of the kerf 33. The arrangement is such that the slag emerging from the cut is confined and cooled by the chill block rolls 3| progressively as the work P is severed. As a result, the slag formation adhering to the work P may be quickly and easily broken or sheared therefrom.

The novel process disclosed herein is primarily intended for use with hot metals at a temperature of 2,000 F. and upwards because the slag problems involved at such high temperatures are acute. However, the invention is not confined for use with such hot metals exclusively since it offers advantages when used in cutting work at lower temperatures.

By the practice of the invention detrimental slag formations are not only eliminated, but by causing the slag to be simultaneously confined and cooled as it emerges from the kerf, removal of all of the slag formed by the thermochemical working process is facilitated. Thus, ferrous metal work, such as bars or slabs, may be rapidly worked or severed, even while hot, without detri mental and undesirable slag formation.

While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is therefore intended and modifications as fall within the true spirit and scope of the invention.

What is claimed is: g

1. Apparatus for controlling molten slag emerging from a kerf formed by thermochemically treating ferrous metal work, comprising a pair of chill members adapted to support the work to be cut adjacent opposite edges of the kerf, said chill members being arranged in spaced divergent relation to'provide space therebetween for receiving the molten slag as it emerges from said kerf.

2. Apparatus for controlling molten slag as it emerges from a kerf formed in a body of ferrous metal by a thermochemical cutting operation with a stream of oxidizing gas adapted progressively to traverse said body along a predetermined path, said apparatus comprising a slag chilling member of metal having one edge disposed in contact with said body near the line of emergence of said slag from said kerf, said slag chilling member also having a. slag receiving surface disposed in laterally offset relation to said path so as not to interfere with said stream as the latter is discharged from said kerf and so that a portion of the slag emerging from the kerf flows over and rapidly hardens by contact with said surface while still connected to said body, with the result that the hardened slag may be sheared or broken readily from said body.

3. Apparatus for controlling molten slag as claimed by claim 2, which is provided with means for cooling said slag chilling member to prevent the heat of said molten slag from damaging said member.

5. Apparatus for controlling molten slag as emerges from a kerf formed in a body of ferrous metal by a thermochemical cutting operation with a stream of oxidizing gas adapted progressively to traverse said body along a predetermined path, said apparatus comprising a pair of slag chilling members mounted in parallel relation to and adjacent opposite sides of said kerf, each of said members having a corresponding edge for contact with said body near the line of emergence of said slag from said kerf, and each of said slag chilling members also having a slag receiving surface disposed in laterally oflset relation to said path so as not to interfere with said stream as the latter is discharged from said kerf and so that a portion of the slag emerging from the kerf flows over and rapidly hardens by contact with said surface while still connected to said body, with the result that the hardened slag may be sheared or broken readily from said body. Y

6. Process of treating slag as it emerges from a kerf formed in a body of ferrous metal by a thermochemical cutting operation with a stream of oxidizing gas adapted progressively to traverse said body along a predetermined path, which comprises causing the molten slag to flow over metal in contact with said body so that said slag is hardened by contact with said member in the form of a sheet while connected to said body,

and then removing said sheet from the edge of said kerf, leaving said edge free of slag.

7. Process of treating molten slag as claimed in claim 6, which includes the step of cooling said member with a fluid to prevent overheating thereof by said molten slag.

8. Process of treating molten slag as claimed in claim 6, which includes the step of moving said heat conductive member responsively to the movement of said stream of oxidizing gas along said path to maintain said member in the desired slag chilling relation to said stream of oxia kerf formed by thermochemically cutting ferand be chilled by a heat conductive member of rous metal work which comprises receiving the slag as it emerges from the kerf between spaced chill members conformed to the shape of and in contact with the work adjacent opposite edges of said kerf.

10. Apparatus for controlling molten slag emerging from a kerf formed by thermochemically cutting ferrous metal work, comprising a pair of chill members adapted to support the work to be cut adjacent opposite edges of such kerf, said chill members being arranged in spaced relation to provide space therebetween for receiving the molten slag as it emerges from said kerf.

- ROGER s. BABCOCK. 

